Chelate ring-closure kinetics of Cr(CO)(5) (DPPM) studied by P-31-NMR spectroscopy

Date

1996-01-01

Author

Özkar, Saim
Tekkaya, A

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P-31-NMR spectroscopy was used to study the kinetics of the chelate ring-closure reaction in Cr(CO)(5) (DPPM) where DPPM is bis (diphenylphosphino)methane. DPPM is potentially a bidentate ligand, but in this complex it is coordinated to the transition metal in a monodentate fashion and therefore can undergo chelation. The thermal chelate ring-closure reaction was carried out in an NMR sample tube at a constant temperature and the course of the reaction was quantitatively followed by taking P-31-NMR spectra in appropriate time intervals. Kinetic results have shown that the chelate ring-closure reaction of Cr(CO)(5) DPPM is of zero-order. Activation parameters were determined by evaluating the kinetic data. The large negative value of the activation entropy implies that the mechanism of the chelate ring-closure reaction is of associative nature in the transition states. The rate determining step might involve both Cr-CO bond breaking and Cr-P bond making. This will generate a seven coordinate transient complex from which the complete detachment of a CO Ligand will lead to the formation of Cr(CO)(4) (DPPM).

Subject Keywords

Tungsten hexacarbonyl, W(co)5l intermediate, Complexes, Ligand, Carbonyl, Photolysis, Mechanism, Catalysis

URI

https://hdl.handle.net/11511/53821

Journal

TURKISH JOURNAL OF CHEMISTRY

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Department of Chemistry, Article

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Citation Formats

S. Özkar and A. Tekkaya, “Chelate ring-closure kinetics of Cr(CO)(5) (DPPM) studied by P-31-NMR spectroscopy,” TURKISH JOURNAL OF CHEMISTRY, pp. 74–79, 1996, Accessed: 00, 2020. [Online]. Available: https://hdl.handle.net/11511/53821.